Herpes simplex virus 1 (HSV) is an important opportunistic pathogen in HIV-1-infected patients as well as the cause of a devastating CNS infection in normal hosts. Although immune responses to HSV have been the subject of intense investigation, the role of immune-mediated pathology in HSV-related brain damage is unknown. In this proposal, the central hypothesis to be tested is that chemokines produced by microglial cells in response to HSV infection initiate a cascade of neuroimmune responses that result in the serious brain damage seen during herpes encephalitis. To test this hypothesis, chemokine production in the brains of HSV-infected mice will be compared to that in cultures of highly purified murine glial and neuronal cells, and in murine organotypic brain slices infected with HSV. This approach will allow us to differentiate microglial cell chemokine production from that of cells of the somatic immune system. Additionally, the use of organotypic brain slice cultures will enable us to specifically deplete microglial cells for "loss-of-function" experiments. We will then investigate the neurotoxic effects of microglial cell-produced immune mediators on cultured murine neurons. Microglia-driven leukocyte trafficking into the brain will be investigated by determining if neutralizing antibodies to chemokines inhibit T-cell infiltration. The neuropathogenic role of T-cell infiltration will be studied by determining if depletion of T-cells in vivo will delay encephalitis and whether adoptive transfer of HSV-specific lymphocytes restores the encephalitis phenotype. Comparing neuropathology in brain slice cultures with and without the transfer of HSV-specific CD4 + and CD8 +lymphocytes, will allow us to distinguish between injury generated by viral infection and brain damage provoked by immunopathogenic mechanisms. Downregulation of microglial cell chemokine production through peripheral benzodiazepine (BDZ) receptor-mediated cellular deactivation will then be examined. We will determine if deactivation of microglia with BDZs suppresses the production of neurotoxic factors. Finally, we will study the effects of BDZ ligands on chemokine production, T-cell trafficking, and the development of encephalitis in vivo. These in vivo, in vitro, and ex vivo models will provide us with the ability to investigate neuropathogenesis, neuroinflammation, neurotoxicity, and neuroimmune-mediated pathology occurring during herpes encephalitis. Knowledge gained from these studies will increase our understanding of the role of microglial cells and chemokine networks that regulate brain inflammation during herpes encephalitis with the ultimate goal of finding new therapy for this serious brain infection. [unreadable] [unreadable] [unreadable]